diff --git a/doc/IR.md b/doc/IR.md
index 2b886c59559..46ff56ec31c 100644
--- a/doc/IR.md
+++ b/doc/IR.md
@@ -527,12 +527,12 @@ Arguments | %value is the value to be stored. %object *must* be of an object typ
 Semantics | Implements ES15 7.3.8 DefinePropertyOrThrow. The instruction follows the rules of JavaScript *own* property access. The property is created or updated in the instance of the object, regardless of whether the same property already exists earlier in the prototype chain.
 Effects | May read and write memory.
 
-### StoreNewOwnPropertyInst
+### DefineNewOwnPropertyInst
 
-StoreNewOwnPropertyInst | _
+DefineNewOwnPropertyInst | _
 --- | --- |
 Description | Create a new *own property* in what is known to be a JavaScript object.
-Example |   `%4 = StoreNewOwnPropertyInst %value, %object, %property, %enumerable : boolean`
+Example |   `%4 = DefineNewOwnPropertyInst %value, %object, %property, %enumerable : boolean`
 Arguments | *%value* is the value to be stored. *%object*, which must be an object, is where the field with name *%property* will be created. *%property* must be a string or index-like number literal, otherwise it is impossible to guarantee that it is new. *%enumerable* determines whether the new property will be created as enumerable or not.
 Semantics | The instruction follows the rules of JavaScript *own* property access. The property is created in the instance of the object, regardless of whether the same property already exists earlier in the prototype chain.
 Effects | May read and write memory.
diff --git a/include/hermes/IR/IRBuilder.h b/include/hermes/IR/IRBuilder.h
index 59f36dea758..ae6f4e0d7be 100644
--- a/include/hermes/IR/IRBuilder.h
+++ b/include/hermes/IR/IRBuilder.h
@@ -446,7 +446,7 @@ class IRBuilder {
       Value *object,
       Value *property,
       PropEnumerable isEnumerable);
-  StoreNewOwnPropertyInst *createStoreNewOwnPropertyInst(
+  DefineNewOwnPropertyInst *createDefineNewOwnPropertyInst(
       Value *storedValue,
       Value *object,
       Literal *property,
diff --git a/include/hermes/IR/Instrs.def b/include/hermes/IR/Instrs.def
index d9d60404e3c..c3f919f6cfe 100644
--- a/include/hermes/IR/Instrs.def
+++ b/include/hermes/IR/Instrs.def
@@ -109,7 +109,7 @@ MARK_LAST(BaseStorePropertyInst)
 
 MARK_FIRST(BaseDefineOwnPropertyInst, Instruction)
 DEF_VALUE(DefineOwnPropertyInst, BaseDefineOwnPropertyInst)
-DEF_VALUE(StoreNewOwnPropertyInst, BaseDefineOwnPropertyInst)
+DEF_VALUE(DefineNewOwnPropertyInst, BaseDefineOwnPropertyInst)
 MARK_LAST(BaseDefineOwnPropertyInst)
 
 DEF_VALUE(DefineOwnGetterSetterInst, Instruction)
diff --git a/include/hermes/IR/Instrs.h b/include/hermes/IR/Instrs.h
index a9963519287..ab80ed0837c 100644
--- a/include/hermes/IR/Instrs.h
+++ b/include/hermes/IR/Instrs.h
@@ -1741,18 +1741,18 @@ class DefineOwnPropertyInst : public BaseDefineOwnPropertyInst {
   }
 };
 
-class StoreNewOwnPropertyInst : public BaseDefineOwnPropertyInst {
-  StoreNewOwnPropertyInst(const StoreNewOwnPropertyInst &) = delete;
-  void operator=(const StoreNewOwnPropertyInst &) = delete;
+class DefineNewOwnPropertyInst : public BaseDefineOwnPropertyInst {
+  DefineNewOwnPropertyInst(const DefineNewOwnPropertyInst &) = delete;
+  void operator=(const DefineNewOwnPropertyInst &) = delete;
 
  public:
-  explicit StoreNewOwnPropertyInst(
+  explicit DefineNewOwnPropertyInst(
       Value *storedValue,
       Value *object,
       Literal *property,
       LiteralBool *isEnumerable)
       : BaseDefineOwnPropertyInst(
-            ValueKind::StoreNewOwnPropertyInstKind,
+            ValueKind::DefineNewOwnPropertyInstKind,
             storedValue,
             object,
             property,
@@ -1766,14 +1766,14 @@ class StoreNewOwnPropertyInst : public BaseDefineOwnPropertyInst {
         "object operand must be known to be an object");
   }
 
-  explicit StoreNewOwnPropertyInst(
-      const StoreNewOwnPropertyInst *src,
+  explicit DefineNewOwnPropertyInst(
+      const DefineNewOwnPropertyInst *src,
       llvh::ArrayRef<Value *> operands)
       : BaseDefineOwnPropertyInst(src, operands) {}
 
   static bool classof(const Value *V) {
     ValueKind kind = V->getKind();
-    return kind == ValueKind::StoreNewOwnPropertyInstKind;
+    return kind == ValueKind::DefineNewOwnPropertyInstKind;
   }
 };
 
diff --git a/include/hermes/Optimizer/PassManager/Passes.def b/include/hermes/Optimizer/PassManager/Passes.def
index 1303b2b63d2..3ab34422068 100644
--- a/include/hermes/Optimizer/PassManager/Passes.def
+++ b/include/hermes/Optimizer/PassManager/Passes.def
@@ -46,7 +46,7 @@ PASS(
 PASS(
     ObjectMergeNewStores,
     "objectmergenewstores",
-    "Merge StoreNewOwnPropertyInsts into AllocObjectLiteral")
+    "Merge DefineNewOwnPropertyInsts into AllocObjectLiteral")
 PASS(SimplifyCFG, "simplifycfg", "Simplify CFG")
 PASS(TypeInference, "typeinference", "Type inference")
 PASS(FunctionAnalysis, "functionanalysis", "Function analysis")
diff --git a/lib/BCGen/HBC/BytecodeGenerator.cpp b/lib/BCGen/HBC/BytecodeGenerator.cpp
index f6d6fa049ce..fd957762a88 100644
--- a/lib/BCGen/HBC/BytecodeGenerator.cpp
+++ b/lib/BCGen/HBC/BytecodeGenerator.cpp
@@ -281,7 +281,7 @@ static bool isIdOperand(const Instruction *I, unsigned idx) {
     CASE_WITH_PROP_IDX(DeletePropertyLooseInst);
     CASE_WITH_PROP_IDX(DeletePropertyStrictInst);
     CASE_WITH_PROP_IDX(LoadPropertyInst);
-    CASE_WITH_PROP_IDX(StoreNewOwnPropertyInst);
+    CASE_WITH_PROP_IDX(DefineNewOwnPropertyInst);
     CASE_WITH_PROP_IDX(StorePropertyLooseInst);
     CASE_WITH_PROP_IDX(StorePropertyStrictInst);
     CASE_WITH_PROP_IDX(TryLoadGlobalPropertyInst);
diff --git a/lib/BCGen/HBC/ISel.cpp b/lib/BCGen/HBC/ISel.cpp
index 17ddac48374..c331c0f631a 100644
--- a/lib/BCGen/HBC/ISel.cpp
+++ b/lib/BCGen/HBC/ISel.cpp
@@ -931,8 +931,8 @@ void HBCISel::generateDefineOwnPropertyInst(
   BCFGen_->emitPutOwnByVal(objReg, valueReg, propReg, Inst->getIsEnumerable());
 }
 
-void HBCISel::generateStoreNewOwnPropertyInst(
-    StoreNewOwnPropertyInst *Inst,
+void HBCISel::generateDefineNewOwnPropertyInst(
+    DefineNewOwnPropertyInst *Inst,
     BasicBlock *next) {
   auto valueReg = encodeValue(Inst->getStoredValue());
   auto objReg = encodeValue(Inst->getObject());
@@ -942,7 +942,7 @@ void HBCISel::generateStoreNewOwnPropertyInst(
   if (auto *numProp = llvh::dyn_cast<LiteralNumber>(prop)) {
     assert(
         isEnumerable &&
-        "No way to generate non-enumerable indexed StoreNewOwnPropertyInst.");
+        "No way to generate non-enumerable indexed DefineNewOwnPropertyInst.");
     uint32_t index = *numProp->convertToArrayIndex();
     if (index <= UINT8_MAX) {
       BCFGen_->emitPutOwnByIndex(objReg, valueReg, index);
diff --git a/lib/BCGen/HBC/LoweringPipelines.cpp b/lib/BCGen/HBC/LoweringPipelines.cpp
index 7b4872ab7a1..49af72ce051 100644
--- a/lib/BCGen/HBC/LoweringPipelines.cpp
+++ b/lib/BCGen/HBC/LoweringPipelines.cpp
@@ -44,7 +44,7 @@ void lowerModuleIR(Module *M, const BytecodeGenerationOptions &options) {
   // as LowerNumericProperties could generate new constants.
   PM.addPass(new LowerNumericProperties());
   // Lower AllocObjectLiteral into a mixture of HBCAllocObjectFromBufferInst,
-  // AllocObjectInst, StoreNewOwnPropertyInst and StorePropertyInst.
+  // AllocObjectInst, DefineNewOwnPropertyInst and StorePropertyInst.
   PM.addPass(new LowerAllocObjectLiteral());
   PM.addPass(new LowerArgumentsArray());
   PM.addPass(new LimitAllocArray(UINT16_MAX));
diff --git a/lib/BCGen/HBC/Passes.cpp b/lib/BCGen/HBC/Passes.cpp
index ff9c3000585..aa4038a0ef2 100644
--- a/lib/BCGen/HBC/Passes.cpp
+++ b/lib/BCGen/HBC/Passes.cpp
@@ -84,11 +84,11 @@ bool LoadConstants::operandMustBeLiteral(Instruction *Inst, unsigned opIndex) {
   if (llvh::isa<SwitchInst>(Inst) && opIndex > 0)
     return true;
 
-  // DefineOwnPropertyInst and StoreNewOwnPropertyInst.
+  // DefineOwnPropertyInst and DefineNewOwnPropertyInst.
   if (auto *SOP = llvh::dyn_cast<BaseDefineOwnPropertyInst>(Inst)) {
     if (opIndex == DefineOwnPropertyInst::PropertyIdx) {
-      if (llvh::isa<StoreNewOwnPropertyInst>(Inst)) {
-        // In StoreNewOwnPropertyInst the property name must be a literal.
+      if (llvh::isa<DefineNewOwnPropertyInst>(Inst)) {
+        // In DefineNewOwnPropertyInst the property name must be a literal.
         return true;
       }
 
diff --git a/lib/BCGen/SH/LoadConstants.cpp b/lib/BCGen/SH/LoadConstants.cpp
index 21a7bcfcd3f..d011226a78d 100644
--- a/lib/BCGen/SH/LoadConstants.cpp
+++ b/lib/BCGen/SH/LoadConstants.cpp
@@ -41,11 +41,11 @@ bool operandMustBeLiteral(Instruction *Inst, unsigned opIndex) {
   if (llvh::isa<SwitchInst>(Inst) && opIndex > 0)
     return true;
 
-  // DefineOwnPropertyInst and StoreNewOwnPropertyInst.
+  // DefineOwnPropertyInst and DefineNewOwnPropertyInst.
   if (auto *SOP = llvh::dyn_cast<BaseDefineOwnPropertyInst>(Inst)) {
     if (opIndex == DefineOwnPropertyInst::PropertyIdx) {
-      if (llvh::isa<StoreNewOwnPropertyInst>(Inst)) {
-        // In StoreNewOwnPropertyInst the property name must be a literal.
+      if (llvh::isa<DefineNewOwnPropertyInst>(Inst)) {
+        // In DefineNewOwnPropertyInst the property name must be a literal.
         return true;
       }
 
diff --git a/lib/BCGen/SH/SH.cpp b/lib/BCGen/SH/SH.cpp
index 22ff6677119..506bdc2292d 100644
--- a/lib/BCGen/SH/SH.cpp
+++ b/lib/BCGen/SH/SH.cpp
@@ -1238,7 +1238,7 @@ class InstrGen {
     generateRegisterPtr(*inst.getStoredValue());
     os_ << ");\n";
   }
-  void generateStoreNewOwnPropertyInst(StoreNewOwnPropertyInst &inst) {
+  void generateDefineNewOwnPropertyInst(DefineNewOwnPropertyInst &inst) {
     os_.indent(2);
     auto prop = inst.getProperty();
     bool isEnumerable = inst.getIsEnumerable();
@@ -1246,7 +1246,7 @@ class InstrGen {
     if (auto *numProp = llvh::dyn_cast<LiteralNumber>(prop)) {
       assert(
           isEnumerable &&
-          "No way to generate non-enumerable indexed StoreNewOwnPropertyInst.");
+          "No way to generate non-enumerable indexed DefineNewOwnPropertyInst.");
       uint32_t index = *numProp->convertToArrayIndex();
       os_ << "_sh_ljs_put_own_by_index(";
       os_ << "shr, ";
diff --git a/lib/IR/IRBuilder.cpp b/lib/IR/IRBuilder.cpp
index ae7b67ea058..fad6df06796 100644
--- a/lib/IR/IRBuilder.cpp
+++ b/lib/IR/IRBuilder.cpp
@@ -622,12 +622,12 @@ DefineOwnPropertyInst *IRBuilder::createDefineOwnPropertyInst(
   insert(SPI);
   return SPI;
 }
-StoreNewOwnPropertyInst *IRBuilder::createStoreNewOwnPropertyInst(
+DefineNewOwnPropertyInst *IRBuilder::createDefineNewOwnPropertyInst(
     Value *storedValue,
     Value *object,
     Literal *property,
     PropEnumerable isEnumerable) {
-  auto *inst = new StoreNewOwnPropertyInst(
+  auto *inst = new DefineNewOwnPropertyInst(
       storedValue,
       object,
       property,
diff --git a/lib/IR/IRVerifier.cpp b/lib/IR/IRVerifier.cpp
index f8433c4d596..5ed018ae109 100644
--- a/lib/IR/IRVerifier.cpp
+++ b/lib/IR/IRVerifier.cpp
@@ -974,23 +974,23 @@ bool Verifier::visitBaseDefineOwnPropertyInst(
 bool Verifier::visitDefineOwnPropertyInst(const DefineOwnPropertyInst &Inst) {
   return visitBaseDefineOwnPropertyInst(Inst);
 }
-bool Verifier::visitStoreNewOwnPropertyInst(
-    const StoreNewOwnPropertyInst &Inst) {
+bool Verifier::visitDefineNewOwnPropertyInst(
+    const DefineNewOwnPropertyInst &Inst) {
   ReturnIfNot(visitBaseDefineOwnPropertyInst(Inst));
   AssertIWithMsg(
       Inst,
       Inst.getObject()->getType().isObjectType(),
-      "StoreNewOwnPropertyInst::Object must be known to be an object");
+      "DefineNewOwnPropertyInst::Object must be known to be an object");
   if (auto *LN = llvh::dyn_cast<LiteralNumber>(Inst.getProperty())) {
     AssertIWithMsg(
         Inst,
         LN->convertToArrayIndex().hasValue(),
-        "StoreNewOwnPropertyInst::Property can only be an index-like number");
+        "DefineNewOwnPropertyInst::Property can only be an index-like number");
   } else {
     AssertIWithMsg(
         Inst,
         llvh::isa<LiteralString>(Inst.getProperty()),
-        "StoreNewOwnPropertyInst::Property must be a string or number literal");
+        "DefineNewOwnPropertyInst::Property must be a string or number literal");
   }
   return true;
 }
diff --git a/lib/IRGen/ESTreeIRGen-expr.cpp b/lib/IRGen/ESTreeIRGen-expr.cpp
index 64cd91ea725..8663c44a4f8 100644
--- a/lib/IRGen/ESTreeIRGen-expr.cpp
+++ b/lib/IRGen/ESTreeIRGen-expr.cpp
@@ -1464,7 +1464,7 @@ Value *ESTreeIRGen::genObjectExpr(ESTree::ObjectExpressionNode *Expr) {
 
   // haveSeenComputedProp tracks whether we have processed a computed property.
   // Once we do, for all future properties, we can no longer generate
-  // StoreNewOwnPropertyInst because the computed property could have already
+  // DefineNewOwnPropertyInst because the computed property could have already
   // defined any property.
   bool haveSeenComputedProp = false;
 
@@ -1564,7 +1564,7 @@ Value *ESTreeIRGen::genObjectExpr(ESTree::ObjectExpressionNode *Expr) {
               Key,
               IRBuilder::PropEnumerable::Yes);
         } else {
-          Builder.createStoreNewOwnPropertyInst(
+          Builder.createDefineNewOwnPropertyInst(
               Builder.getLiteralNull(),
               Obj,
               Key,
@@ -1629,7 +1629,7 @@ Value *ESTreeIRGen::genObjectExpr(ESTree::ObjectExpressionNode *Expr) {
         Builder.createDefineOwnPropertyInst(
             value, Obj, Key, IRBuilder::PropEnumerable::Yes);
       } else {
-        Builder.createStoreNewOwnPropertyInst(
+        Builder.createDefineNewOwnPropertyInst(
             value, Obj, Key, IRBuilder::PropEnumerable::Yes);
       }
       propValue->state = PropertyValue::IRGenerated;
@@ -1690,7 +1690,7 @@ Value *ESTreeIRGen::genTypedObjectExpr(
         "Missing stored value in typechecked object literal");
     // Use a literal if possible, otherwise use the default init value.
     // Avoid putting non-literals here because we want to emit PrStore
-    // instead of StoreNewOwnPropertyInst.
+    // instead of DefineNewOwnPropertyInst.
     Value *initValue = nullptr;
     if (llvh::isa<Literal>(it->second.first)) {
       initValue = it->second.first;
diff --git a/lib/IRGen/ESTreeIRGen.cpp b/lib/IRGen/ESTreeIRGen.cpp
index adcaf1d6947..03020df4158 100644
--- a/lib/IRGen/ESTreeIRGen.cpp
+++ b/lib/IRGen/ESTreeIRGen.cpp
@@ -1066,7 +1066,7 @@ void ESTreeIRGen::emitRestProperty(
         Builder.createAllocObjectLiteralInst({}, Builder.getLiteralNull());
 
     for (Literal *key : literalExcludedItems)
-      Builder.createStoreNewOwnPropertyInst(
+      Builder.createDefineNewOwnPropertyInst(
           zeroValue, excludedObj, key, IRBuilder::PropEnumerable::Yes);
 
     for (Value *key : computedExcludedItems) {
diff --git a/lib/Optimizer/Scalar/ObjectMergeNewStores.cpp b/lib/Optimizer/Scalar/ObjectMergeNewStores.cpp
index 5d48e81847e..1d4fed2cf70 100644
--- a/lib/Optimizer/Scalar/ObjectMergeNewStores.cpp
+++ b/lib/Optimizer/Scalar/ObjectMergeNewStores.cpp
@@ -8,7 +8,7 @@
 //===----------------------------------------------------------------------===//
 /// \file
 ///
-/// This optimization collects StoreNewOwnPropertyInsts and merges them into a
+/// This optimization collects DefineNewOwnPropertyInsts and merges them into a
 /// single AllocObjectLiteral.
 //===----------------------------------------------------------------------===//
 
@@ -25,8 +25,8 @@
 namespace hermes {
 namespace {
 
-/// Define a type for managing lists of StoreNewOwnPropertyInsts.
-using StoreList = llvh::SmallVector<StoreNewOwnPropertyInst *, 4>;
+/// Define a type for managing lists of DefineNewOwnPropertyInsts.
+using StoreList = llvh::SmallVector<DefineNewOwnPropertyInst *, 4>;
 /// Define a type for mapping a given basic block to the stores to a given
 /// AllocObjectLiteralInst in that basic block.
 using BlockUserMap = llvh::DenseMap<BasicBlock *, StoreList>;
@@ -42,11 +42,11 @@ StoreList collectStores(
       DI, allocInst->getParent(), [&userBasicBlockMap](BasicBlock *BB) {
         return userBasicBlockMap.find(BB) != userBasicBlockMap.end();
       });
-  // Iterate over the sorted blocks to collect StoreNewOwnPropertyInst users
+  // Iterate over the sorted blocks to collect DefineNewOwnPropertyInst users
   // until we encounter a nullptr indicating we should stop.
   StoreList instrs;
   for (BasicBlock *BB : sortedBlocks) {
-    for (StoreNewOwnPropertyInst *I : userBasicBlockMap.find(BB)->second) {
+    for (DefineNewOwnPropertyInst *I : userBasicBlockMap.find(BB)->second) {
       // If I is null, we cannot consider additional stores.
       if (!I)
         return instrs;
@@ -56,7 +56,7 @@ StoreList collectStores(
   return instrs;
 }
 
-/// Merge StoreNewOwnPropertyInsts into a single AllocObjectLiteralInst.
+/// Merge DefineNewOwnPropertyInsts into a single AllocObjectLiteralInst.
 /// Non-literal values are set with placeholders and later patched with the
 /// correct value.
 /// \p allocInst the instruction to transform
@@ -78,7 +78,7 @@ bool mergeStoresToObjectLiteral(
   // Keep track of if we have encountered a numeric key yet.
   bool hasSeenNumericKey = false;
   for (uint32_t i = 0; i < size; ++i) {
-    StoreNewOwnPropertyInst *I = users[i];
+    DefineNewOwnPropertyInst *I = users[i];
     Literal *propKey = llvh::cast<Literal>(I->getProperty());
     auto *propVal = I->getStoredValue();
     hasSeenNumericKey |= llvh::isa<LiteralNumber>(propKey);
@@ -124,24 +124,26 @@ bool mergeNewStores(Function *F) {
   auto tryAdd =
       [](AllocObjectLiteralInst *A, Instruction *U, StoreList &stores) {
         // If the store list has been terminated by a nullptr, we have already
-        // encountered a non-SNOP user of A in this block. Ignore this user.
+        // encountered a non-define new user of A in this block. Ignore this
+        // user.
         if (!stores.empty() && !stores.back())
           return;
-        auto *SI = llvh::dyn_cast<StoreNewOwnPropertyInst>(U);
-        if (!SI || SI->getStoredValue() == A || !SI->getIsEnumerable()) {
-          // A user that's not a StoreNewOwnPropertyInst storing into the object
-          // created by allocInst. We have to stop processing here. Note that we
-          // check the stored value instead of the target object so that we omit
-          // the case where an object is stored into itself. While it should
-          // technically be safe, this maintains the invariant that stop as soon
-          // the allocated object is used as something other than the target of
-          // a StoreNewOwnPropertyInst.
+        auto *newDef = llvh::dyn_cast<DefineNewOwnPropertyInst>(U);
+        if (!newDef || newDef->getStoredValue() == A ||
+            !newDef->getIsEnumerable()) {
+          // A user that's not a DefineNewOwnPropertyInst storing into the
+          // object created by allocInst. We have to stop processing here. Note
+          // that we check the stored value instead of the target object so that
+          // we omit the case where an object is stored into itself. While it
+          // should technically be safe, this maintains the invariant that stop
+          // as soon the allocated object is used as something other than the
+          // target of a DefineNewOwnPropertyInst.
           stores.push_back(nullptr);
         } else {
           assert(
-              SI->getObject() == A &&
-              "SNOP using allocInst must use it as object or value");
-          stores.push_back(SI);
+              newDef->getObject() == A &&
+              "DefineNew using allocInst must use it as object or value");
+          stores.push_back(newDef);
         }
       };
 
@@ -152,8 +154,8 @@ bool mergeNewStores(Function *F) {
     for (Instruction &I : BB) {
       for (size_t i = 0; i < I.getNumOperands(); ++i) {
         if (auto *A = llvh::dyn_cast<AllocObjectLiteralInst>(I.getOperand(i))) {
-          // For now, we only consider merging StoreNewOwnPropertyInsts that are
-          // writing into an empty object to start.
+          // For now, we only consider merging DefineNewOwnPropertyInsts that
+          // are writing into an empty object to start.
           if (A->getKeyValuePairCount() == 0)
             tryAdd(A, &I, allocUsers[A][&BB]);
         }
diff --git a/lib/Optimizer/Scalar/TypeInference.cpp b/lib/Optimizer/Scalar/TypeInference.cpp
index be95753f980..e5aac644cc6 100644
--- a/lib/Optimizer/Scalar/TypeInference.cpp
+++ b/lib/Optimizer/Scalar/TypeInference.cpp
@@ -565,7 +565,7 @@ class TypeInferenceImpl {
   Type inferDefineOwnPropertyInst(DefineOwnPropertyInst *inst) {
     return Type::createNoType();
   }
-  Type inferStoreNewOwnPropertyInst(StoreNewOwnPropertyInst *inst) {
+  Type inferDefineNewOwnPropertyInst(DefineNewOwnPropertyInst *inst) {
     return Type::createNoType();
   }
 
diff --git a/test/BCGen/HBC/hbc_object_literals-lowering.js b/test/BCGen/HBC/hbc_object_literals-lowering.js
index 7f0db2fda28..ca0cf4a73dc 100644
--- a/test/BCGen/HBC/hbc_object_literals-lowering.js
+++ b/test/BCGen/HBC/hbc_object_literals-lowering.js
@@ -117,7 +117,7 @@ function accessorObjectLiteral(func) {
 // IRGEN-NEXT:  %4 = HBCLoadConstInst (:string) "c": string
 // IRGEN-NEXT:       DefineOwnGetterSetterInst %2: object, %3: undefined, %0: object, %4: string, true: boolean
 // IRGEN-NEXT:  %6 = HBCLoadConstInst (:null) null: null
-// IRGEN-NEXT:       StoreNewOwnPropertyInst %6: null, %0: object, "d": string, true: boolean
+// IRGEN-NEXT:       DefineNewOwnPropertyInst %6: null, %0: object, "d": string, true: boolean
 // IRGEN-NEXT:       ReturnInst %0: object
 // IRGEN-NEXT:function_end
 
diff --git a/test/BCGen/HBC/own_properties.js b/test/BCGen/HBC/own_properties.js
index 52d73726344..53eb9a43f2f 100644
--- a/test/BCGen/HBC/own_properties.js
+++ b/test/BCGen/HBC/own_properties.js
@@ -7,7 +7,7 @@
 
 // RUN: %hermes -O0 -target=HBC -dump-lir %s | %FileCheckOrRegen --match-full-lines %s
 
-// Test that StoreNewOwnPropertyInst is lowered to DefineOwnPropertyInst when
+// Test that DefineNewOwnPropertyInst is lowered to DefineOwnPropertyInst when
 // the property name is a valid array index.
 // We use a computed key to avoid emitting AllocObjectLiteral.
 
@@ -41,13 +41,13 @@ function foo() {
 // CHECK-NEXT:  %1 = CreateScopeInst (:environment) %VS1: any, %0: environment
 // CHECK-NEXT:  %2 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %3 = HBCLoadConstInst (:number) 1: number
-// CHECK-NEXT:       StoreNewOwnPropertyInst %3: number, %2: object, "a": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst %3: number, %2: object, "a": string, true: boolean
 // CHECK-NEXT:  %5 = HBCLoadConstInst (:number) 2: number
-// CHECK-NEXT:       StoreNewOwnPropertyInst %5: number, %2: object, 10: number, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst %5: number, %2: object, 10: number, true: boolean
 // CHECK-NEXT:  %7 = HBCLoadConstInst (:number) 3: number
-// CHECK-NEXT:       StoreNewOwnPropertyInst %7: number, %2: object, 11: number, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst %7: number, %2: object, 11: number, true: boolean
 // CHECK-NEXT:  %9 = HBCLoadConstInst (:number) 4: number
-// CHECK-NEXT:        StoreNewOwnPropertyInst %9: number, %2: object, "999999999999999999999999": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst %9: number, %2: object, "999999999999999999999999": string, true: boolean
 // CHECK-NEXT:  %11 = HBCLoadConstInst (:number) 5: number
 // CHECK-NEXT:        DefineOwnPropertyInst %11: number, %2: object, 42: number, true: boolean
 // CHECK-NEXT:        ReturnInst %2: object
diff --git a/test/IRGen/__proto__-permitted-dup.js b/test/IRGen/__proto__-permitted-dup.js
index e6e64b12218..c0ec7c3559a 100644
--- a/test/IRGen/__proto__-permitted-dup.js
+++ b/test/IRGen/__proto__-permitted-dup.js
@@ -99,8 +99,8 @@ function protoDupAccessor3(func) {
 // CHECK-NEXT:  %6 = AllocObjectLiteralInst (:object) %5: any
 // CHECK-NEXT:       StoreFrameInst %1: environment, %6: object, [%VS2.?obj]: object
 // CHECK-NEXT:  %8 = CreateFunctionInst (:object) %1: environment, %__proto__(): functionCode
-// CHECK-NEXT:       StoreNewOwnPropertyInst %8: object, %6: object, "__proto__": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst 42: number, %6: object, "a": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst %8: object, %6: object, "__proto__": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst 42: number, %6: object, "a": string, true: boolean
 // CHECK-NEXT:        ReturnInst %6: object
 // CHECK-NEXT:function_end
 
@@ -115,11 +115,11 @@ function protoDupAccessor3(func) {
 // CHECK-NEXT:  %4 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:       StoreFrameInst %1: environment, %4: object, [%VS3.?obj]: object
 // CHECK-NEXT:  %6 = CreateFunctionInst (:object) %1: environment, %"__proto__ 1#"(): functionCode
-// CHECK-NEXT:       StoreNewOwnPropertyInst %6: object, %4: object, "__proto__": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst %6: object, %4: object, "__proto__": string, true: boolean
 // CHECK-NEXT:  %8 = LoadFrameInst (:any) %1: environment, [%VS3.func]: any
 // CHECK-NEXT:  %9 = CallInst (:any) %8: any, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined
 // CHECK-NEXT:  %10 = CallBuiltinInst (:any) [HermesBuiltin.silentSetPrototypeOf]: number, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined, %4: object, %9: any
-// CHECK-NEXT:        StoreNewOwnPropertyInst 42: number, %4: object, "a": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst 42: number, %4: object, "a": string, true: boolean
 // CHECK-NEXT:        ReturnInst %4: object
 // CHECK-NEXT:function_end
 
diff --git a/test/IRGen/__proto__-shorthand.js b/test/IRGen/__proto__-shorthand.js
index 8d53c400570..224f2fac7bf 100644
--- a/test/IRGen/__proto__-shorthand.js
+++ b/test/IRGen/__proto__-shorthand.js
@@ -73,9 +73,9 @@ function protoShorthandMix2(func) {
 // CHECK-NEXT:       StoreFrameInst %1: environment, 42: number, [%VS1.__proto__]: any
 // CHECK-NEXT:  %6 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %7 = LoadFrameInst (:any) %1: environment, [%VS1.__proto__]: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst %7: any, %6: object, "__proto__": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 2: number, %6: object, "a": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst 3: number, %6: object, "b": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst %7: any, %6: object, "__proto__": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 2: number, %6: object, "a": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst 3: number, %6: object, "b": string, true: boolean
 // CHECK-NEXT:        ReturnInst %6: object
 // CHECK-NEXT:function_end
 
@@ -91,7 +91,7 @@ function protoShorthandMix2(func) {
 // CHECK-NEXT:       StoreFrameInst %1: environment, 42: number, [%VS2.__proto__]: any
 // CHECK-NEXT:  %6 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %7 = LoadFrameInst (:any) %1: environment, [%VS2.__proto__]: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst null: null, %6: object, "__proto__": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst null: null, %6: object, "__proto__": string, true: boolean
 // CHECK-NEXT:  %9 = LoadFrameInst (:any) %1: environment, [%VS2.__proto__]: any
 // CHECK-NEXT:        DefineOwnPropertyInst %9: any, %6: object, "__proto__": string, true: boolean
 // CHECK-NEXT:        ReturnInst %6: object
@@ -109,7 +109,7 @@ function protoShorthandMix2(func) {
 // CHECK-NEXT:       StoreFrameInst %1: environment, 42: number, [%VS3.__proto__]: any
 // CHECK-NEXT:  %6 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %7 = LoadFrameInst (:any) %1: environment, [%VS3.__proto__]: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst %7: any, %6: object, "__proto__": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst %7: any, %6: object, "__proto__": string, true: boolean
 // CHECK-NEXT:  %9 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %10 = CallBuiltinInst (:any) [HermesBuiltin.silentSetPrototypeOf]: number, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined, %6: object, %9: object
 // CHECK-NEXT:        ReturnInst %6: object
@@ -128,6 +128,6 @@ function protoShorthandMix2(func) {
 // CHECK-NEXT:  %6 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %7 = AllocObjectLiteralInst (:object) %6: object
 // CHECK-NEXT:  %8 = LoadFrameInst (:any) %1: environment, [%VS4.__proto__]: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst %8: any, %7: object, "__proto__": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst %8: any, %7: object, "__proto__": string, true: boolean
 // CHECK-NEXT:        ReturnInst %7: object
 // CHECK-NEXT:function_end
diff --git a/test/IRGen/__proto__.js b/test/IRGen/__proto__.js
index 23b0628d51e..c3a0bca2d7b 100644
--- a/test/IRGen/__proto__.js
+++ b/test/IRGen/__proto__.js
@@ -71,8 +71,8 @@ function protoIsDynamic(func, getParent) {
 // CHECK-NEXT:  %4 = LoadFrameInst (:any) %1: environment, [%VS1.func]: any
 // CHECK-NEXT:  %5 = CallInst (:any) %4: any, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined
 // CHECK-NEXT:  %6 = AllocObjectLiteralInst (:object) %5: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst 2: number, %6: object, "a": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 3: number, %6: object, "b": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 2: number, %6: object, "a": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 3: number, %6: object, "b": string, true: boolean
 // CHECK-NEXT:       ReturnInst %6: object
 // CHECK-NEXT:function_end
 
@@ -83,7 +83,7 @@ function protoIsDynamic(func, getParent) {
 // CHECK-NEXT:  %0 = GetParentScopeInst (:environment) %VS0: any, %parentScope: environment
 // CHECK-NEXT:  %1 = CreateScopeInst (:environment) %VS2: any, %0: environment
 // CHECK-NEXT:  %2 = AllocObjectLiteralInst (:object) null: null
-// CHECK-NEXT:       StoreNewOwnPropertyInst 2: number, %2: object, "a": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 2: number, %2: object, "a": string, true: boolean
 // CHECK-NEXT:       ReturnInst %2: object
 // CHECK-NEXT:function_end
 
@@ -94,7 +94,7 @@ function protoIsDynamic(func, getParent) {
 // CHECK-NEXT:  %0 = GetParentScopeInst (:environment) %VS0: any, %parentScope: environment
 // CHECK-NEXT:  %1 = CreateScopeInst (:environment) %VS3: any, %0: environment
 // CHECK-NEXT:  %2 = AllocObjectLiteralInst (:object) 10: number
-// CHECK-NEXT:       StoreNewOwnPropertyInst 3: number, %2: object, "b": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 3: number, %2: object, "b": string, true: boolean
 // CHECK-NEXT:       ReturnInst %2: object
 // CHECK-NEXT:function_end
 
@@ -105,7 +105,7 @@ function protoIsDynamic(func, getParent) {
 // CHECK-NEXT:  %0 = GetParentScopeInst (:environment) %VS0: any, %parentScope: environment
 // CHECK-NEXT:  %1 = CreateScopeInst (:environment) %VS4: any, %0: environment
 // CHECK-NEXT:  %2 = AllocObjectLiteralInst (:object) null: null
-// CHECK-NEXT:       StoreNewOwnPropertyInst 4: number, %2: object, "c": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 4: number, %2: object, "c": string, true: boolean
 // CHECK-NEXT:       ReturnInst %2: object
 // CHECK-NEXT:function_end
 
@@ -122,8 +122,8 @@ function protoIsDynamic(func, getParent) {
 // CHECK-NEXT:  %6 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %7 = LoadFrameInst (:any) %1: environment, [%VS5.func]: any
 // CHECK-NEXT:  %8 = CallInst (:any) %7: any, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined
-// CHECK-NEXT:       StoreNewOwnPropertyInst %8: any, %6: object, "a": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst 10: number, %6: object, "b": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst %8: any, %6: object, "a": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst 10: number, %6: object, "b": string, true: boolean
 // CHECK-NEXT:  %11 = LoadFrameInst (:any) %1: environment, [%VS5.getParent]: any
 // CHECK-NEXT:  %12 = CallInst (:any) %11: any, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined
 // CHECK-NEXT:  %13 = CallBuiltinInst (:any) [HermesBuiltin.silentSetPrototypeOf]: number, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined, %6: object, %12: any
diff --git a/test/IRGen/accessors.js b/test/IRGen/accessors.js
index eae7fbcce3f..ed5d698ffd6 100644
--- a/test/IRGen/accessors.js
+++ b/test/IRGen/accessors.js
@@ -29,13 +29,13 @@ var x = {
 // CHECK-NEXT:  %2 = AllocStackInst (:any) $?anon_0_ret: any
 // CHECK-NEXT:       StoreStackInst undefined: undefined, %2: any
 // CHECK-NEXT:  %4 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst null: null, %4: object, "1": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst null: null, %4: object, "1": string, true: boolean
 // CHECK-NEXT:  %6 = CreateFunctionInst (:object) %0: environment, %"get a"(): functionCode
 // CHECK-NEXT:       DefineOwnGetterSetterInst %6: object, undefined: undefined, %4: object, "a": string, true: boolean
 // CHECK-NEXT:  %8 = CreateFunctionInst (:object) %0: environment, %"get 1"(): functionCode
 // CHECK-NEXT:  %9 = CreateFunctionInst (:object) %0: environment, %"set 1"(): functionCode
 // CHECK-NEXT:        DefineOwnGetterSetterInst %8: object, %9: object, %4: object, "1": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst null: null, %4: object, "b": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst null: null, %4: object, "b": string, true: boolean
 // CHECK-NEXT:        DefineOwnPropertyInst 12: number, %4: object, "b": string, true: boolean
 // CHECK-NEXT:        StorePropertyLooseInst %4: object, globalObject: object, "x": string
 // CHECK-NEXT:  %14 = LoadStackInst (:any) %2: any
diff --git a/test/IRGen/array_object.js b/test/IRGen/array_object.js
index fc7438ae87d..b1178d34327 100644
--- a/test/IRGen/array_object.js
+++ b/test/IRGen/array_object.js
@@ -45,9 +45,9 @@ function foo(param) {
 // CHECK-NEXT:       StoreFrameInst %1: environment, undefined: undefined, [%VS1.obj]: any
 // CHECK-NEXT:       StoreFrameInst %1: environment, undefined: undefined, [%VS1.foo]: any
 // CHECK-NEXT:  %6 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst 2: number, %6: object, "1": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 2: number, %6: object, "1": string, true: boolean
 // CHECK-NEXT:  %8 = LoadFrameInst (:any) %1: environment, [%VS1.param]: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst %8: any, %6: object, "key": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst %8: any, %6: object, "key": string, true: boolean
 // CHECK-NEXT:        StoreFrameInst %1: environment, %6: object, [%VS1.obj]: any
 // CHECK-NEXT:  %11 = AllocArrayInst (:object) 4: number, 1: number, 2: number, 3: number, 4: number
 // CHECK-NEXT:        StoreFrameInst %1: environment, %11: object, [%VS1.foo]: any
diff --git a/test/IRGen/es6/object-computed-destructuring.js b/test/IRGen/es6/object-computed-destructuring.js
index 7c894d278c8..7366ccfce94 100644
--- a/test/IRGen/es6/object-computed-destructuring.js
+++ b/test/IRGen/es6/object-computed-destructuring.js
@@ -34,7 +34,7 @@ var {} = x;
 // CHECK-NEXT:  %10 = LoadPropertyInst (:any) %9: any, "a": string
 // CHECK-NEXT:        StorePropertyLooseInst %10: any, globalObject: object, "b": string
 // CHECK-NEXT:  %12 = AllocObjectLiteralInst (:object) null: null
-// CHECK-NEXT:        StoreNewOwnPropertyInst 0: number, %12: object, "a": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst 0: number, %12: object, "a": string, true: boolean
 // CHECK-NEXT:  %14 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %15 = CallBuiltinInst (:any) [HermesBuiltin.copyDataProperties]: number, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined, %14: object, %9: any, %12: object
 // CHECK-NEXT:        StorePropertyLooseInst %15: any, globalObject: object, "rest": string
@@ -46,7 +46,7 @@ var {} = x;
 // CHECK-NEXT:  %22 = LoadPropertyInst (:any) %17: any, "c": string
 // CHECK-NEXT:        StorePropertyLooseInst %22: any, globalObject: object, "d": string
 // CHECK-NEXT:  %24 = AllocObjectLiteralInst (:object) null: null
-// CHECK-NEXT:        StoreNewOwnPropertyInst 0: number, %24: object, "c": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst 0: number, %24: object, "c": string, true: boolean
 // CHECK-NEXT:        StorePropertyLooseInst 0: number, %24: object, %19: any
 // CHECK-NEXT:  %27 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %28 = CallBuiltinInst (:any) [HermesBuiltin.copyDataProperties]: number, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined, %27: object, %17: any, %24: object
diff --git a/test/IRGen/es6/rest-property.js b/test/IRGen/es6/rest-property.js
index 00e814ac687..7f4de9c1524 100644
--- a/test/IRGen/es6/rest-property.js
+++ b/test/IRGen/es6/rest-property.js
@@ -99,8 +99,8 @@ function f5(o) {
 // CHECK-NEXT:  %10 = LoadPropertyInst (:any) %7: any, "b": string
 // CHECK-NEXT:        StoreFrameInst %1: environment, %10: any, [%VS2.b]: any
 // CHECK-NEXT:  %12 = AllocObjectLiteralInst (:object) null: null
-// CHECK-NEXT:        StoreNewOwnPropertyInst 0: number, %12: object, "a": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst 0: number, %12: object, "b": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst 0: number, %12: object, "a": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst 0: number, %12: object, "b": string, true: boolean
 // CHECK-NEXT:  %15 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %16 = CallBuiltinInst (:any) [HermesBuiltin.copyDataProperties]: number, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined, %15: object, %7: any, %12: object
 // CHECK-NEXT:        StoreFrameInst %1: environment, %16: any, [%VS2.rest]: any
@@ -122,7 +122,7 @@ function f5(o) {
 // CHECK-NEXT:  %7 = LoadPropertyInst (:any) %6: any, "a": string
 // CHECK-NEXT:       StoreFrameInst %1: environment, %7: any, [%VS3.a]: any
 // CHECK-NEXT:  %9 = AllocObjectLiteralInst (:object) null: null
-// CHECK-NEXT:        StoreNewOwnPropertyInst 0: number, %9: object, "a": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst 0: number, %9: object, "a": string, true: boolean
 // CHECK-NEXT:  %11 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %12 = CallBuiltinInst (:any) [HermesBuiltin.copyDataProperties]: number, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined, %11: object, %6: any, %9: object
 // CHECK-NEXT:        StoreFrameInst %1: environment, %12: any, [%VS3.rest]: any
@@ -145,7 +145,7 @@ function f5(o) {
 // CHECK-NEXT:       StoreFrameInst %1: environment, %8: any, [%VS4.a]: any
 // CHECK-NEXT:  %10 = LoadFrameInst (:any) %1: environment, [%VS4.o]: any
 // CHECK-NEXT:  %11 = AllocObjectLiteralInst (:object) null: null
-// CHECK-NEXT:        StoreNewOwnPropertyInst 0: number, %11: object, "a": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst 0: number, %11: object, "a": string, true: boolean
 // CHECK-NEXT:  %13 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %14 = CallBuiltinInst (:any) [HermesBuiltin.copyDataProperties]: number, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined, %13: object, %7: any, %11: object
 // CHECK-NEXT:        StorePropertyLooseInst %14: any, %10: any, "rest": string
@@ -168,7 +168,7 @@ function f5(o) {
 // CHECK-NEXT:  %9 = LoadPropertyInst (:any) %6: any, "a": string
 // CHECK-NEXT:        StoreFrameInst %1: environment, %9: any, [%VS5.a]: any
 // CHECK-NEXT:  %11 = AllocObjectLiteralInst (:object) null: null
-// CHECK-NEXT:        StoreNewOwnPropertyInst 0: number, %11: object, "a": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst 0: number, %11: object, "a": string, true: boolean
 // CHECK-NEXT:  %13 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %14 = CallBuiltinInst (:any) [HermesBuiltin.copyDataProperties]: number, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined, %13: object, %6: any, %11: object
 // CHECK-NEXT:        StoreFrameInst %1: environment, %14: any, [%VS5.rest]: any
diff --git a/test/IRGen/es6/spread-operator.js b/test/IRGen/es6/spread-operator.js
index 8e28a4a950a..3601f0bee4b 100644
--- a/test/IRGen/es6/spread-operator.js
+++ b/test/IRGen/es6/spread-operator.js
@@ -41,7 +41,7 @@ function foo(a, b, c) {
 // CHECK-NEXT:       StoreFrameInst %1: environment, %6: any, [%VS1.c]: any
 // CHECK-NEXT:  %8 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %9 = LoadFrameInst (:any) %1: environment, [%VS1.a]: any
-// CHECK-NEXT:        StoreNewOwnPropertyInst %9: any, %8: object, "a": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst %9: any, %8: object, "a": string, true: boolean
 // CHECK-NEXT:  %11 = LoadFrameInst (:any) %1: environment, [%VS1.b]: any
 // CHECK-NEXT:  %12 = CallBuiltinInst (:any) [HermesBuiltin.copyDataProperties]: number, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined, %8: object, %11: any
 // CHECK-NEXT:  %13 = LoadFrameInst (:any) %1: environment, [%VS1.c]: any
diff --git a/test/IRGen/es6/tagged-template.js b/test/IRGen/es6/tagged-template.js
index fd6da76585a..6209cebbe6d 100644
--- a/test/IRGen/es6/tagged-template.js
+++ b/test/IRGen/es6/tagged-template.js
@@ -190,7 +190,7 @@ function helloWorld() {
 // CHECK-NEXT:       StoreFrameInst %1: environment, undefined: undefined, [%VS7.obj]: any
 // CHECK-NEXT:  %3 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %4 = LoadPropertyInst (:any) globalObject: object, "dummy": string
-// CHECK-NEXT:       StoreNewOwnPropertyInst %4: any, %3: object, "func": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst %4: any, %3: object, "func": string, true: boolean
 // CHECK-NEXT:       StoreFrameInst %1: environment, %3: object, [%VS7.obj]: any
 // CHECK-NEXT:  %7 = GetTemplateObjectInst (:any) 5: number, true: boolean, "hello world!": string
 // CHECK-NEXT:  %8 = LoadFrameInst (:any) %1: environment, [%VS7.obj]: any
diff --git a/test/IRGen/json.js b/test/IRGen/json.js
index b5479b97e67..8fb691dd2b7 100644
--- a/test/IRGen/json.js
+++ b/test/IRGen/json.js
@@ -45,26 +45,26 @@ var json = {
 // CHECK-NEXT:       StoreStackInst undefined: undefined, %2: any
 // CHECK-NEXT:  %4 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %5 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst "example glossary": string, %5: object, "title": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst "example glossary": string, %5: object, "title": string, true: boolean
 // CHECK-NEXT:  %7 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst "S": string, %7: object, "title": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst "S": string, %7: object, "title": string, true: boolean
 // CHECK-NEXT:  %9 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %10 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:        StoreNewOwnPropertyInst "SGML": string, %10: object, "ID": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst "SGML": string, %10: object, "SortAs": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst "Standard Generalized Markup Language": string, %10: object, "GlossTerm": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst "SGML": string, %10: object, "Acronym": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst "ISO 8879:1986": string, %10: object, "Abbrev": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst "SGML": string, %10: object, "ID": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst "SGML": string, %10: object, "SortAs": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst "Standard Generalized Markup Language": string, %10: object, "GlossTerm": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst "SGML": string, %10: object, "Acronym": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst "ISO 8879:1986": string, %10: object, "Abbrev": string, true: boolean
 // CHECK-NEXT:  %16 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:        StoreNewOwnPropertyInst "A meta-markup language, used to create markup languages such as DocBook.": string, %16: object, "para": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst "A meta-markup language, used to create markup languages such as DocBook.": string, %16: object, "para": string, true: boolean
 // CHECK-NEXT:  %18 = AllocArrayInst (:object) 2: number, "GML": string, "XML": string
-// CHECK-NEXT:        StoreNewOwnPropertyInst %18: object, %16: object, "GlossSeeAlso": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst %16: object, %10: object, "GlossDef": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst "markup": string, %10: object, "GlossSee": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst %10: object, %9: object, "GlossEntry": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst %9: object, %7: object, "GlossList": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst %7: object, %5: object, "GlossDiv": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst %5: object, %4: object, "glossary": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst %18: object, %16: object, "GlossSeeAlso": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst %16: object, %10: object, "GlossDef": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst "markup": string, %10: object, "GlossSee": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst %10: object, %9: object, "GlossEntry": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst %9: object, %7: object, "GlossList": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst %7: object, %5: object, "GlossDiv": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst %5: object, %4: object, "glossary": string, true: boolean
 // CHECK-NEXT:        StorePropertyLooseInst %4: object, globalObject: object, "json": string
 // CHECK-NEXT:  %27 = LoadStackInst (:any) %2: any
 // CHECK-NEXT:        ReturnInst %27: any
diff --git a/test/IRGen/object_literals.js b/test/IRGen/object_literals.js
index 2099c713fb7..15ed352527c 100644
--- a/test/IRGen/object_literals.js
+++ b/test/IRGen/object_literals.js
@@ -118,9 +118,9 @@ function accessorObjectLiteral2(func) {
 // CHECK-NEXT:  %2 = LoadParamInst (:any) %func: any
 // CHECK-NEXT:       StoreFrameInst %1: environment, %2: any, [%VS1.func]: any
 // CHECK-NEXT:  %4 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst 10: number, %4: object, "prop1": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 10: number, %4: object, "prop1": string, true: boolean
 // CHECK-NEXT:  %6 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst 10: number, %6: object, "prop1": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 10: number, %6: object, "prop1": string, true: boolean
 // CHECK-NEXT:       ReturnInst undefined: undefined
 // CHECK-NEXT:function_end
 
@@ -133,12 +133,12 @@ function accessorObjectLiteral2(func) {
 // CHECK-NEXT:  %2 = LoadParamInst (:any) %func: any
 // CHECK-NEXT:       StoreFrameInst %1: environment, %2: any, [%VS2.func]: any
 // CHECK-NEXT:  %4 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst 1: number, %4: object, "a": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 2: number, %4: object, "b": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 3: number, %4: object, "c": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 4: number, %4: object, "d": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 5: number, %4: object, "5": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst 6: number, %4: object, "6": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 1: number, %4: object, "a": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 2: number, %4: object, "b": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 3: number, %4: object, "c": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 4: number, %4: object, "d": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 5: number, %4: object, "5": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst 6: number, %4: object, "6": string, true: boolean
 // CHECK-NEXT:        ReturnInst %4: object
 // CHECK-NEXT:function_end
 
@@ -151,13 +151,13 @@ function accessorObjectLiteral2(func) {
 // CHECK-NEXT:  %2 = LoadParamInst (:any) %func: any
 // CHECK-NEXT:       StoreFrameInst %1: environment, %2: any, [%VS3.func]: any
 // CHECK-NEXT:  %4 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst 10: number, %4: object, "a": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 10: number, %4: object, "a": string, true: boolean
 // CHECK-NEXT:  %6 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst 100: number, %6: object, "1": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 200: number, %6: object, "2": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst %6: object, %4: object, "b": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst "hello": string, %4: object, "c": string, true: boolean
-// CHECK-NEXT:        StoreNewOwnPropertyInst null: null, %4: object, "d": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 100: number, %6: object, "1": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 200: number, %6: object, "2": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst %6: object, %4: object, "b": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst "hello": string, %4: object, "c": string, true: boolean
+// CHECK-NEXT:        DefineNewOwnPropertyInst null: null, %4: object, "d": string, true: boolean
 // CHECK-NEXT:        ReturnInst %4: object
 // CHECK-NEXT:function_end
 
@@ -170,10 +170,10 @@ function accessorObjectLiteral2(func) {
 // CHECK-NEXT:  %2 = LoadParamInst (:any) %func: any
 // CHECK-NEXT:       StoreFrameInst %1: environment, %2: any, [%VS4.func]: any
 // CHECK-NEXT:  %4 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst 1: number, %4: object, "a": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 2: number, %4: object, "b": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst null: null, %4: object, "d": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 3: number, %4: object, "c": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 1: number, %4: object, "a": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 2: number, %4: object, "b": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst null: null, %4: object, "d": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 3: number, %4: object, "c": string, true: boolean
 // CHECK-NEXT:       DefineOwnPropertyInst 4: number, %4: object, "d": string, true: boolean
 // CHECK-NEXT:        ReturnInst %4: object
 // CHECK-NEXT:function_end
@@ -199,9 +199,9 @@ function accessorObjectLiteral2(func) {
 // CHECK-NEXT:  %2 = LoadParamInst (:any) %func: any
 // CHECK-NEXT:       StoreFrameInst %1: environment, %2: any, [%VS6.func]: any
 // CHECK-NEXT:  %4 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst 1: number, %4: object, "a": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 2: number, %4: object, "b": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 3: number, %4: object, "c": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 1: number, %4: object, "a": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 2: number, %4: object, "b": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 3: number, %4: object, "c": string, true: boolean
 // CHECK-NEXT:  %8 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %9 = CallBuiltinInst (:any) [HermesBuiltin.silentSetPrototypeOf]: number, empty: any, false: boolean, empty: any, undefined: undefined, undefined: undefined, %4: object, %8: object
 // CHECK-NEXT:        ReturnInst %4: object
@@ -217,9 +217,9 @@ function accessorObjectLiteral2(func) {
 // CHECK-NEXT:       StoreFrameInst %1: environment, %2: any, [%VS7.func]: any
 // CHECK-NEXT:  %4 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %5 = AllocObjectLiteralInst (:object) %4: object
-// CHECK-NEXT:       StoreNewOwnPropertyInst 1: number, %5: object, "a": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 2: number, %5: object, "b": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 3: number, %5: object, "c": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 1: number, %5: object, "a": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 2: number, %5: object, "b": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 3: number, %5: object, "c": string, true: boolean
 // CHECK-NEXT:       ReturnInst %5: object
 // CHECK-NEXT:function_end
 
@@ -232,9 +232,9 @@ function accessorObjectLiteral2(func) {
 // CHECK-NEXT:  %2 = LoadParamInst (:any) %func: any
 // CHECK-NEXT:       StoreFrameInst %1: environment, %2: any, [%VS8.func]: any
 // CHECK-NEXT:  %4 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst 1: number, %4: object, "a": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 2: number, %4: object, "b": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 3: number, %4: object, "c": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 1: number, %4: object, "a": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 2: number, %4: object, "b": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 3: number, %4: object, "c": string, true: boolean
 // CHECK-NEXT:       DefineOwnPropertyInst 4: number, %4: object, "test": string, true: boolean
 // CHECK-NEXT:       ReturnInst %4: object
 // CHECK-NEXT:function_end
@@ -249,8 +249,8 @@ function accessorObjectLiteral2(func) {
 // CHECK-NEXT:       StoreFrameInst %1: environment, %2: any, [%VS9.func]: any
 // CHECK-NEXT:       StoreFrameInst %1: environment, undefined: undefined, [%VS9.obj]: any
 // CHECK-NEXT:  %5 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst 10: number, %5: object, "a": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 20: number, %5: object, "b": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 10: number, %5: object, "a": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 20: number, %5: object, "b": string, true: boolean
 // CHECK-NEXT:       StoreFrameInst %1: environment, %5: object, [%VS9.obj]: any
 // CHECK-NEXT:  %9 = AllocObjectLiteralInst (:object) empty: any
 // CHECK-NEXT:  %10 = LoadFrameInst (:any) %1: environment, [%VS9.obj]: any
@@ -268,10 +268,10 @@ function accessorObjectLiteral2(func) {
 // CHECK-NEXT:  %2 = LoadParamInst (:any) %func: any
 // CHECK-NEXT:       StoreFrameInst %1: environment, %2: any, [%VS10.func]: any
 // CHECK-NEXT:  %4 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst 10: number, %4: object, "a": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst "test-str": string, %4: object, "b": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst null: null, %4: object, "c": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst null: null, %4: object, "d": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 10: number, %4: object, "a": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst "test-str": string, %4: object, "b": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst null: null, %4: object, "c": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst null: null, %4: object, "d": string, true: boolean
 // CHECK-NEXT:       DefineOwnPropertyInst 10086: number, %4: object, "c": string, true: boolean
 // CHECK-NEXT:        ReturnInst %4: object
 // CHECK-NEXT:function_end
@@ -285,11 +285,11 @@ function accessorObjectLiteral2(func) {
 // CHECK-NEXT:  %2 = LoadParamInst (:any) %func: any
 // CHECK-NEXT:       StoreFrameInst %1: environment, %2: any, [%VS11.func]: any
 // CHECK-NEXT:  %4 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst 10: number, %4: object, "a": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst "test-str": string, %4: object, "b": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 10: number, %4: object, "a": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst "test-str": string, %4: object, "b": string, true: boolean
 // CHECK-NEXT:  %7 = CreateFunctionInst (:object) %1: environment, %"get c"(): functionCode
 // CHECK-NEXT:       DefineOwnGetterSetterInst %7: object, undefined: undefined, %4: object, "c": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst null: null, %4: object, "d": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst null: null, %4: object, "d": string, true: boolean
 // CHECK-NEXT:        ReturnInst %4: object
 // CHECK-NEXT:function_end
 
diff --git a/test/IRGen/own_props.js b/test/IRGen/own_props.js
index e0a1f0368c8..a13815dbc1a 100644
--- a/test/IRGen/own_props.js
+++ b/test/IRGen/own_props.js
@@ -19,8 +19,8 @@
 // CHECK-NEXT:  %1 = AllocStackInst (:any) $?anon_0_ret: any
 // CHECK-NEXT:       StoreStackInst undefined: undefined, %1: any
 // CHECK-NEXT:  %3 = AllocObjectLiteralInst (:object) empty: any
-// CHECK-NEXT:       StoreNewOwnPropertyInst null: null, %3: object, "10": string, true: boolean
-// CHECK-NEXT:       StoreNewOwnPropertyInst 2: number, %3: object, "11": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst null: null, %3: object, "10": string, true: boolean
+// CHECK-NEXT:       DefineNewOwnPropertyInst 2: number, %3: object, "11": string, true: boolean
 // CHECK-NEXT:       DefineOwnPropertyInst 3: number, %3: object, "10": string, true: boolean
 // CHECK-NEXT:       StoreStackInst %3: object, %1: any
 // CHECK-NEXT:  %8 = LoadStackInst (:any) %1: any